These breast cancers have distinct biological features: among individuals with gBRCA1m, breast cancers are typically hormone receptor-negative (~76%) and human epidermal growth factor receptor 2 (HER2)-negative (94%), while breast cancers developing in individuals with gBRCA2m are more frequently hormone receptor-positive (83%) and HER2-negative (89%)14. This evidence concerns the gene ERBB2 and breast cancer.